An electrocardiogram (ECG)-triggered, magnetization-prepared, segmented, 3D true fast imaging with steady-state precession (true-FISP) sequence with fat saturation was recently proposed for coronary artery imaging. A magnetization preparation scheme consisting of an ␣/2 radiofrequency (RF) pulse followed by 20 constant flip angle dummy RF cycles was used to reduce signal oscillations in the approach to steady state. However, if large resonance offsets on the order of 70 -100 Hz are present, significant magnetization oscillations will still occur during data acquisition, which will result in image ghosting and blurring. The goal of this work was to validate that a linear flip angle (LFA) series can be used during magnetization preparation to reduce these image artifacts. Computer simulations, phantom studies, and coronary artery imaging in healthy volunteers were performed to compare this magnetization preparation scheme with that of an ␣ An electrocardiogram (ECG)-triggered, magnetization prepared, segmented, 3D true fast imaging with steady-state precession (true-FISP) sequence was recently developed for imaging the coronary arteries (1,2). For coronary imaging, the requirement of fat saturation and ECG triggering demands that the data be acquired during the transient period, when the magnetization approaches steady state after a trigger delay time and the fat saturation prepulse in each cardiac cycle. However, if the spins are not at the resonant frequency, magnetization oscillations during data acquisition cause signal fluctuations in k-space, which consequently lead to image artifacts such as ghosting and blurring.Several methods, such as ␣/2 (␣ ϭ data acquisition radiofrequency (RF) pulse flip angle) preparation (3), catalyzation (4), and magnetization preparation using variable flip angles (5), have been proposed to reduce the transient magnetization oscillations in true-FISP and enable data acquisition during the initial RF cycles before establishment of steady state. The ␣/2 preparation works well for spins that are on-resonance, but the magnetization continues to oscillate for spins that are not at the resonant frequency. The catalyzation approach has been shown to improve the signal response over a wide range of offresonance frequencies and to be relatively insensitive to T 1 and T 2 variations. A practical limitation of this method is the requirement of a good slice profile of the frequencyselective RF pulses, because the effectiveness of the method is dependent on B 1 field homogeneity. Nishimura et al. (5) The purpose of this work was to evaluate the effectiveness of a linear flip angle (LFA) preparation scheme in reducing the image artifacts in coronary artery imaging using 3D true-FISP. The LFA preparation was compared to the magnetization preparation method of an ␣/2 pulse followed by constant flip angle preparation cycles (1). Computer simulations, phantom studies, and volunteer studies were performed. Using simulations, the signal oscillations with the LFA preparation were evaluated with varia...

Following administration of Gd-DTPA, infarcted myocardium exhibits delayed enhancement and can be imaged using an inversion-recovery sequence. A conventional segmented acquisition requires a number of breath-holds to image the heart. Single-shot phase-sensitive inversion-recovery (PSIR) true-FISP may be combined with parallel imaging using SENSE to achieve high spatial resolution. SNR may be improved by averaging multiple motion-corrected images acquired during free breathing. PSIR techniques have demonstrated a number of benefits including consistent contrast and appearance over a relatively wide range of inversion recovery times (TI), improved contrast-to-noise ratio, and consistent size of the enhanced region. Comparison between images acquired using segmented breath-held turbo-FLASH and averaged, motion-corrected, free-breathing true-FISP show excellent agreement of measured CNR and infarct size. In this study, motion correction was implemented using image registration postprocessing rather than navigator correction of individual frames. Myocardial viability assessment using Gd-DTPA enhancement MRI is gaining clinical acceptance (1,2). Using recent MRI methods (3) myocardial infarction (MI) may be imaged with high spatial resolution and good contrast. Following administration of Gd-DTPA, infarcted myocardium exhibits delayed enhancement and can be imaged using an inversion-recovery (IR) sequence (1-3). Using a conventional segmented acquisition requires a number of breathholds to image the heart. This paper introduces a method for free-breathing acquisition of delayed enhancement imaging and a quantitative evaluation is presented. Single-shot IR true-FISP may be combined with parallel imaging using SENSE to achieve high spatial resolution (4,5) comparable to conventional segmented IR turbo-FLASH. A single-shot acquisition eliminates the requirement for breath-holding. A phasesensitive inversion-recovery (PSIR) method (6) combined with parallel imaging reconstruction was used. PSIR techniques have demonstrated a number of benefits including consistent contrast and appearance over a relatively wide range of inversion recovery times (TI), improved contrastto-noise ratio (CNR), and accurate depiction of the enhanced region. Enhanced signal-to-noise ratio (SNR) may be achieved by averaging multiple motion-corrected images acquired during free breathing. Multiple free-breathing images were motion corrected using a multiscale, subpixel, intensity-based image registration method (7,8). Image registration was constrained to rigid body transformation.Averaged free-breathing images were compared with images acquired using a standard breath-held segmented IR turbo-FLASH sequence. While true-FISP has a ͌(T 2 /T 1 ) dependence in steady state, Scheffler and Hennig (9) have shown that inversion recovery with true-FISP readout closely follows the predicted T 1 -weighted recovery and is actually more accurate than the standard IR turbo-FLASH. Comparison between the two sequences included measurement of CNR between normal and...

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Purpose: To evaluate the effectiveness of flow-sensitive dephasing (FSD) magnetization preparation in improving blood signal suppression of three-dimensional (3D) turbo spin-echo (TSE) sequence (SPACE) for isotropic high-spatial-resolution carotid arterial wall imaging at 3T. Materials and Methods:The FSD-prepared SPACE sequence (FSD-SPACE) was implemented by adding two identical FSD gradient pulses right before and after the first refocusing 180 -pulse of the SPACE sequence in all three orthogonal directions. Nine healthy volunteers were imaged at 3T with SPACE, FSD-SPACE, and multislice T2-weighted 2D TSE coupled with saturation band (SB-TSE). Apparent carotid wall-lumen contrast-to-noise ratio (aCNR w-l ) and apparent lumen area (aLA) at the locations with residualblood (rb) signal shown on SPACE images were compared between SPACE and FSD-SPACE. Carotid aCNR w-l and lumen (LA) and wall area (WA) measured from FSD-SPACE were compared to those measured from SB-TSE.Results: Plaque-mimicking flow artifacts identified in seven carotids on SPACE images were eliminated on FSD-SPACE images. The FSD preparation resulted in slightly reduced aCNR w-l (P ¼ 0.025), but significantly improved aCNR between the wall and rb regions (P < 0.001) and larger aLA (P < 0.001). Compared to SB-TSE, FSD-SPACE offered comparable aCNR w-l with much higher spatial resolution, shorter imaging time, and larger artery coverage. The LA and WA measurements from the two techniques were in good agreement based on intraclasss correlation coefficient (0.988 and 0.949, respectively; P < 0.001) and Bland-Altman analyses.Conclusion: FSD-SPACE is a time-efficient 3D imaging technique for carotid arterial wall with superior spatial resolution and blood signal suppression.